Transcription

Down Bromley Kent

Nov. 26th

My dear Gray

The very day after my last letter yours of Novr. 10th
& the Review in Silliman, which I feared might have been lost, reached me. We were all very much interested by the political part of your
letter: in some odd way one never feels that information & opinions
printed in a newspaper come from a living source; they seem dead, whereas all
that you write is full of life.— Many thanks for P.S. about maize; if
the husked form had been the aboriginal, it would surely have not varied so readily;
there must be some mistake in statement of Indian, quoted by Aug. St.
Hilaire.— The Reviews interested me
profoundly; you rashly ask for my opinion & you must
consequently endure a long letter.

First for Dimorphism: I do not at present like the
term ``Diœcio-dimorphism''; for I think it gives quite false notion, that the
phenomena are connected with a separation of the sexes.
Certainly in Primula there is unequal fertility in the two forms, & I suspect
this is case with Linum; & therefore I felt bound in Primula paper to
state that it might be a step towards dioicous condition;
though I believe there are no dioicous forms in Primulaceæ or Linaceæ. But
the three forms in Lythrum convince me that the phenomenon is in
no way necessarily connected with any tendency to separation of sexes. The case seems to me in result or function to be almost identical with what old
C. K. Sprengel called ``dichogamy'',
& which is so frequent in truly hermaphrodite groups; namely the pollen
& stigma of each flower being mature at different periods. If I am right it is
very advisable not to use term ``diœcious'' as this at once brings notion of
separation of sexes.— I hope you will be able to attend a little to Plantago;
I can hardly understand the sentence in your article. In
which form does stigma project in bud (this occurs in long-styled Lythrum,
but is not then fertilised)? is the short-styled
(i.e. your long-stamened) really sterile? You will think that I am in the most
unpleasant, contradictory, fractious humour, when I tell you that I do not like your
term of ``precocious fertilisation'' for your second class of
dimorphism. If I can trust my memory, the state
of corolla, of stigma & pollen-grains is different from state of parts
in bud; that they are in a condition of special modification. But upon my
life I am ashamed of myself to differ so much from my betters on this head.—
The temporary theory which I have formed on this class of Dimorphism, just to
guide experiment, is that the perfect flowers can only be perfectly fertilised
by insects & are in this case abundantly crossed; but that
the flowers are not always, especially in early spring, visited
enough by insects, & therefore the little imperfect self-fertilising
flowers are developed to ensure a sufficiency of seed for present generations. Viola canina is sterile, when not visited by insects, but when
so visited forms plenty of seed. I infer from
structure of 3 or 4 forms of Balsamineæ
that these require insects; at least there is almost as plain adaptation to insects as
in Orchids.— I have Oxalis acetosella ready in pots
for experiment next spring; & I fear this will upset
my little theory; unless I can as Hooker says ``Oh you will wriggle out of
anything''.— Campanula carpathica, as I proved
this summer, is absolutely sterile if insects are excluded. Specularia speculum is
fairly fertile when enclosed; & this seemed to me to be effected by the frequent
closing of the flower; the inward angular folds of corolla corresponding with
the clefts of the open stigma, & in this action pushing pollen from
outside of stigma on to its surface. Now can you tell me,
does Spec. perfoliata close its flower like S. speculum with angular
inward folds; if so, I am smashed without some fearful
``wriggling''.— Are the imperfect flowers of your Specularia the
early or the later ones? very early or very late? It is rather pretty to see importance
of closing of flowers of Sp. speculum.—

I entirely agree with you in your remarks on the part which crossing plays. I was much perplexed by Oliver's remarks in N. Hist
Review of the Primula case, on the lower plants having sexes more often separated than
in the higher plants,—so exactly the reverse of what takes place in
animals.— Hooker in Review of Orchids repeats
this remark. There seems to me much truth in what you say,
& it did not occur to me, about no improbability of specilisation in
certain lines in lowly organised beings. I could hardly doubt that the
Hermaphroditic state is the aboriginal one. But how is it in the conjugation of
Confervæ—is not one of the two individuals here in fact male
& the other female?? I have been much puzzled by this
contrast in sexual arrangements between plants & animals. Can there be anything
in following consideration. By roughest calculation about 13 of British genera of aquatic plants belong to Linnean
classes of Mono- & Diœcia; whilst of terrestrial plants (the aquatic
genera being substracted) only 113 of genera belong to these two classes. Is there any truth in this fact
generally? Can aquatic plants, being confined to a small area or small
community of individuals, require more free crossing & therefore have separate
sexes?

But to return to one point; does not Alph. Decandolle say that aquatic plants taken as
a whole are lowly organised compared with terrestrial;
& may not Oliver's remark on separation of sexes in lowly organised plants stand
in some relation to their being frequently aquatic? Or is this all rubbish?

I have left myself little room for orchids & indeed I have little to
say except to express my admiration at clearness & ingenuity with which you
explain & describe all the forms. It seems
to me all excellently done, & has interested me beyond measure.— Do
your Platantheras smell sweetest at night; this I suspect is clear guide that moths are
the fertilisers.— I have been especially interested by case of
P. psycodes, more especially since the D. of Argyll's contemptuous
remarks on my case of Angræcum, which in action seems analogous to your
case.

But by far the most wonderful is the case of G. tridentata; I hope you will
confirm so remarkable a physiological fact. If I understand
rightly the rostellum alone is penetrated,—the part primordially of a
stigmatic nature. In this observation you have anticipated an experiment, which I mean
to try, whether pollen-tubes will penetrate the great rostellum of
Cattleya.— I daresay you are quite right about
self-fertilisation being much commoner than I thought with orchids. Did I tell you that I have found in Neottia nidus avis that this ensues, if in
course of few days the flowers are not visited by insects.?

Your observations on Cypripedium seem excellent; & I daresay I am wholly
wrong; it seems to me now more likely that small insects
should lick juice off hairs with jaws or short proboscis, than with long proboscis. How
curious about the little bristles on the stigma! What a magnificent compliment you end
your Review with! You & Hooker seem determined to
turn my head with conceit & vanity (if not already turned) & make me an
unbearable wretch.—

P.S. | In my last letter, I mentioned Bates' paper: he is a man of lowly origin, of great force of character, & wonderfully
self-educated, but constitutionally of low spirits & poor & under
unpleasant circumstances of life. Could you induce any of your Zoological co-editors,
just to notice his paper (& if so inform me); it
would be a good & charitable deed, for it would encourage & please a
man, that wants & deserves encouragement.

What a fearfully long letter I have written!

P.S. 2d. Would you be so kind as to tell me whether Fragaria
vesca & Virginiana differ much Botanically for I cannot make out that
any one has succeeded in crossing them.—

I have just had long letter from Hooker on part which crossing plays in Nature; I must
consider it well, & see if it alters my notions.—

The year is established by the relationship to the letter from Asa Gray,
10 November 1862. CD refers in his second postscript to having
received the letter from J. D. Hooker,
26 November 1862; since Joseph Dalton Hooker's letter could not have
arrived at Down before 27 November 1862, the second postscript must
have been added on the latter date. From Gray's reply (see letter from Asa Gray,
9 December 1862), it appears that this letter was sent in the same
envelope as the letter to Asa Gray, 23 November [1862]; however, since the two
letters have separate salutations and valedictions, they have been treated separately.

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f2 3830.f2

In his letter of 10 November 1862, Gray had enclosed proof-sheets
of a portion of the November 1862 number of the
American Journal
of Science and Arts (commonly known as
`Silliman's journal', after its founder Benjamin Silliman), which included Gray's
follow-up article to his review of Orchids (A. Gray 1862b).
See also letter to Asa Gray, 23 November [1862].

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f3 3830.f3

CD refers to a postscript to the letter from Asa Gray,
10 November 1862, that is now missing. In his letter of
16 October [1862], CD had asked Gray about a report that, under cultivation,
the bracts of wild maize had been found to decrease in size. CD here refers to the claim
of a young Guarany Indian, reported by Auguste Saint-Hilaire, that Zea mays
grew wild in the humid forests of his native Paraguay (A. de
Candolle 1855, 2: 951). In Variation 1: 320--1, CD stated: A peculiar kind [of maize], in which the grains, instead of being naked,
are concealed by husks as much as eleven times in length, has been stated on
insufficient evidence to grow wild in Brazil. It is almost certain that the aboriginal
form would have had its grains thus protected; but the seeds of the Brazilian variety
produce, as I hear from Professor Asa Gray, and as is stated in two published
accounts, either common or husked maize; and it is not credible that a wild species,
when first cultivated, should vary so quickly and in so great a degree.

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f4 3830.f4

See n. 2, above. In addition to A. Gray 1862b, the
November 1862 number of the
American Journal of Science and
Arts included
A. Gray 1862e (see n. 5, below).

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f5 3830.f5

A. Gray 1862e.

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f6 3830.f6

The phenomenon now known as heterostyly, the occurrence of which CD had described in
his paper `Dimorphic condition in Primula', had earlier been termed
`dioecio-dimorphism' by Gray and John Torrey (Torrey and Gray 1838--43, 2:
38--9). See also letters from Asa Gray, [10 July 1860]
(Correspondence vol. 8) and 11 October 1861
(Correspondence vol. 9). Gray used the term in his discussion of
dimorphism in the American Journal of Science and Arts
(A. Gray 1862e, p. 419).

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f7 3830.f7

`Dimorphic condition in Primula', p. 95 (Collected papers
2: 61--2). In the conclusion to his later paper, `Two forms in species of
Linum', p. 83 (Collected papers 2: 105), CD stated:
That in some cases this dimorphism may be a step towards a
complete separation of the sexes, I will not dispute; but good reasons could be
assigned to show that there is no necessary connexion between reciprocal dimorphism
and a tendency to dioecious structure. Although good is gained by the inevitable
crossing of the dimorphic flowers, yet numerous other analogous facts lead me to
conclude that some other quite unknown law of nature is here dimly indicated to us.

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f8 3830.f8

In `Three forms of Lythrum salicaria', which was read before the Linnean
Society on 16 June 1864, CD stated: As some authors
consider reciprocal dimorphism to be the first stage toward dioeciousness, the
difficulty of understanding how a trimorphic plant like Lythrum salicaria
could become dioecious should be noticed; and as dimorphism and trimorphism are so
closely allied, it is not probable that either state is necessarily in any way related
to a separation of the sexes—though it may occasionally lead to this end.

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f9 3830.f9

C. K. Sprengel 1793. CD's heavily annotated copy of this work is
in the Darwin Library--CUL (Marginalia 1: 774--85).

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f10 3830.f10

In A. Gray 1862e, p. 419, Gray stated that two principal
kinds of dimorphism had been noticed by botanists. The first of these, he noted, he had
called `diœcio-dimorphism' (now called heterostyly). Before discussing
the second kind, which he called `precocious fertilization' (now called cleistogamy), he
commented: The diœcio-dimorphous species of
Plantago had seemed to confuse this case with the next. That is, the
short-stamened flowers appeared to be fertilized in the closed flower, and the
long-stamened and generally sterile plants therefore to be generally useless
… a recent observation on a single specimen
… shows the top of the style projecting from the tip of the closed
corolla. This refers the case to the same category with Houstonia,
Primula, &c. See also letter from Asa Gray,
29 December 1862, and Correspondence vol. 11, letter
to Asa Gray, 19 January [1863].

CD's notes of his observations on Viola canina, made in May 1862,
are in DAR 111: 3--5. See also letter to J. D. Hooker, 30 May [1862],
letter to W. E. Darwin, [31 May 1862], and letter to
Asa Gray, 10--20 June [1862]. Gray wrote on CD's letter `But Viola
goes on all summer'; see letter from Asa Gray, 29 December 1862.

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f15 3830.f15

CD refers to several species of Balsaminaceae sent to him by Hooker in
October 1862 (see letter to Daniel Oliver, 13 October [1862], letter
to J. D. Hooker, 14 [October 1862], and letter from
J. D. Hooker, [18 October 1862]).

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f16 3830.f16

See letter to Asa Gray, 10--20 June [1862] and n. 24. CD had
cultivated plants of Oxalis acetosella with a view to testing a possible case
of heterostyly, but later decided that the species was not heterostyled (see letters to
Daniel Oliver, 20 [April 1862] and 24 April [1862], and letter to
J. D. Hooker, 30 May [1862]). There are notes on his
experiments on the cleistogamic flowers of Oxalis acetosella, made in the
spring of 1863, in DAR 109 (ser. 2): 6.

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f17 3830.f17

See letter from J. D. Hooker, 7 November 1862,
n. 17.

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f18 3830.f18

CD's notes of his observations on Campanula carpathica and
Specularia
speculum, dated 4 October 1862, are
in DAR 79: 113. These observations are recorded in
Cross and self fertilisation, p. 174.

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f19 3830.f19

CD had repeatedly asked Gray for information regarding Specularia speculum
since learning from him that it had cleistogamic flowers (see letters from Asa Gray,
11 October 1861 (Correspondence vol. 9),
2--3 July 1862, 18--19 August 1862, and
5 September 1862, and letters to Asa Gray, 10--20 June
[1862], 23[--4] July [1862], and [3--]4 September [1862]). CD marked the last
three sentences of this paragraph with a marginal line, apparently in order to draw
Gray's attention to his request.

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f20 3830.f20

In his review, Gray criticised a point in Daniel Oliver's anonymous review of CD's
paper, published in the Natural History Review ([Oliver] 1862c). Oliver had
referred in his review (p. 236; see also p. 238) to two kinds of
dimorphism: one that was `apparently favourable to variation, marked primarily by a
partial or complete separation of the sexes' (i.e., heterostyly), and one that was
`conservative, and unfavourable to variation', with the sexual organs of certain flowers
to some extent enclosed and sealed up (i.e., cleistogamy). In
A. Gray 1862e, p. 420, Gray commented: we were somewhat surprised at finding that the reviewer of Darwin's
Primula-paper in the Natural History Review … regards the
separation of sexes, and therefore cross-fertilization, as favouring variation, and
self-fertilization as necessarily inimical to it. This probably comes from not
considering that while close-breeding tends to keep a given form true—in
virtue of the ordinary likeness of offspring to parents—it equally and in
the same way tends to perpetuate a variation once originated from that form, and also,
along with selection (natural or artificial), to educe and further develope or confirm
said variety. On the other hand, free cross-breeding of incipient varieties
inter
se and with their original types is just the way to
blend all together, to repress all salient characteristics as fast as the mysterious
process of variation originates them, and fuse the whole into a homogeneous form.

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f21 3830.f21

In considering the apparent tendency in Primula towards a separation of the
sexes, Oliver raised the question `why did they ever become hermaphrodite?' ([Oliver]
1862c, p. 238). He went on to say: While we may
… suggest that certain species are tending to a separation of the
sexes, we must not forget that arguments may be advanced to shew that it is not
impossible but that they may be striving towards more perfect hermaphroditism,
especially if we bring to mind the evidence … furnished by the
`Geological Record.' This evidence does certainly appear in favour of a greater
predominance of unisexual forms at an early period than obtains at the present day.
Gray responded to this in A. Gray 1862e, p. 420,
stating: on morphological grounds, we should look upon
hermaphroditism, rather than the contrary, as the normal or primary condition of
flowers, and enquire how and why so many became diclinous … Forms
which are low in the scale as respects morphological completeness may be high in the
scale of rank founded on specialization of structure and functions. See
also letter to Daniel Oliver, 15 April [1862] and n. 3.

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f22 3830.f22

[J. D. Hooker] 1862d, p. 371.

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f23 3830.f23

CD refers to filamentous green algae.

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f24 3830.f24

The reference is probably to A. de Candolle 1855, a heavily
annotated copy of which is in the Darwin Library--CUL (see Marginalia 1:
106--53).

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f25 3830.f25

CD refers to Gray's follow-up article to his review of Orchids
(A. Gray 1862b), in which he detailed a number of his observations on
North American orchid species.

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f26 3830.f26

In his article, Gray noted that Platanthera psycodes had a long and curved
nectary (A. Gray 1862b, p. 425). In his review of
Orchids, George Douglas Campbell, eighth duke of Argyll, had questioned CD's
conclusion that a moth with an unusually long proboscis must be responsible for the
pollination of Angraecum sesquipedale, in view of its similarly long nectary
([G. D. Campbell] 1862, pp. 394--5; see Orchids,
pp. 197--203).

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f27 3830.f27

Gray had introduced his description of Gymnadenia tridentata with the
comment: `we hesitate to bring forward our too scanty observations until another summer
affords an opportunity to test them' (A. Gray 1862b, p. 426);
he confirmed his observations in A. Gray 1863a, pp. 293--4. See also
letters from Asa Gray, 18--19 August 1862 and
22 September 1862. CD made undated notes referring to Gray's account
of this species (DAR 70: 8, 17), and cited Gray's observations in `Fertilization of
orchids', p. 147 (Collected papers 2: 144).

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f28 3830.f28

CD suggested to John Scott that he might carry out this experiment on
Cattleya, in the letter to John Scott, 3 December [1862].

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f29 3830.f29

In Orchids, CD sought to demonstrate that the `main object' of the various
`contrivances by which Orchids are fertilised' was to ensure cross-fertilisation. He
noted only one exception (p. 359). In A. Gray 1862b,
p. 426, Gray repeated his earlier description (A. Gray 1862c,
p. 259--60) of the occurrence of self-pollination in
Platanthera
hyperborea and Gymnadenia tridentata, noting:
`Natura non agit
saltatim, and is more flexible and diversified
in her ways than we are apt to think: many other cases of occasional or habitual
self-fertilization may be expected among Orchids.' CD included the two species mentioned
by Gray on an undated list of `self-fertilisers' that is now in DAR 70: 167, and
included a modified discussion of the occurrence of self-pollination in orchids in
Orchids 2d ed., pp. 288--93.

Gray concluded his article by expressing his gratitude to CD for `having brought
back teleological considerations into botany' (A. Gray 1862b, p. 428).
He continued (p. 429): In this fascinating book on the
fertilization of Orchids and in his paper explaining the meaning of dimorphism in
hermaphrodite flowers, Mr. Darwin,—who does not pretend to be a
botanist—has given new eyes to botanists, and inaugurated a new era in the
science.

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f33 3830.f33

Bates 1862a. See letter to Asa Gray, 23 November [1862].

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f34 3830.f34

Gray was one of the botanical editors of the
American Journal of Science and
Arts; Gray reviewed
Bates 1862a in the journal in September 1863
(A. Gray 1863b). See also letter from H. W. Bates,
24 November 1862, and letter to H. W. Bates,
25 November [1862].

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f35 3830.f35

CD was preparing a draft of the part of Variation dealing with `Facts of
variation of Plants' (Variation 1: 305--72; see `Journal'
(Correspondence vol. 10, Appendix II)). In his account of strawberries
(Variation 1: 351--4), CD noted that the European and American species could be
crossed `with some difficulty', but considered it `improbable that hybrids sufficiently
fertile to be worth cultivation will ever be thus produced.' He continued
(p. 352): `This fact is surprising, as these forms structurally are not widely
distinct, and are sometimes connected in the districts where they grow wild, as I hear
from Professor Asa Gray, by puzzling intermediate forms.'